1. Field of the Invention
The present invention relates to a small-sized and thin type resolver using a sheet coil, which is used for detection of speed and position of a servomotor in the field of, for example, factory automation equipment and office automation apparatuses, and is composed of a sheet coil.
2. Description of the Related Art
A prior art with resolver using a sheet coil is such that a flat sheet coil of an excitation phase consisting of one phase and a flat sheet coil of a detection phase consisting of two phases are disposed with air gaps, wherein the detection phase has a detection phase of eddy current patterns made of copper foil and formed on the surface side and rear side thereof, between which a thin film insulation sheet layer is placed, and another detection phase having a phase difference of an electric angle of 90xc2x0 with respect to the above-described detection phase, although it is the same pattern, between which the thin insulation sheet layer is placed. On the other hand, the excitation phase is such that the same eddy-like pattern is disposed without any difference in phase on the surface side and rear side thereof, between which a thin-film insulation sheet layer is placed. The resolver using a sheet coil is such that the flux linkage of the detection changes according to a sine wave by a rotation angle at high precision on the basis of an eddy pattern that is accurately patterned by etching, etc., and the angular error is reduced to be small (For example, JP, 8-84449, A).
Also, the following rotary transformer is disclosed as that having the same functions as those of the resolver using a sheet coil. In the rotary transformer, a pair of secondary side conductor patterns formed on the surface side and rear side of a thin-film substrate made of an insulation body are formed of multi-layered thin-film conductors concentrically with clearance secured at a part of a circle, and the ends between the thin-film conductors are connected to each other by a jumper line, wherein the second side is opposed to and disposed at the primary side of the transformer through a throughhole and clearance (For example, JP, 8-306562, A).
Also, in other prior art with resolvers having a sheet coil, there is a resolver in which a patter of a rotary transformer is provided inside the resolver pattern, and the pattern of the rotary transformer and that of the resolver are made integral with each other (For example, JP, 8-136211, A).
However, the following problems and shortcomings exist in the prior art. (1) Because a resolver using a rotary transformer according to JP, 8-136211 is such that the pattern of a rotary transformer is made integral with that of a resolver, the number of working processes can be reduced, and production cost thereof can be decreased. But, the outer diameter must be reduced when making the resolver smaller, the pattern of the rotary transformer is made very small, wherein a lowering in the transformation ratio occurs due to a decrease in a magnetic flux and number of windings, and an appointed detection voltage could not be obtained. Also, because the detection phase pattern links with a magnetic flux produced by the rotary transformer, large residual voltage is generated to cause an angular error to be increased. (2) In the resolver described in JP, 8-84449 and rotary transformer described in JP, 8-306562 the primary side center is misaligned with the secondary side center due to misalignment when attaching a sheet coil of a conductor, and as the sheet coil rotates, a fluctuation component in the mechanical angle of 360xc2x0 appeared in the amplitude of flux linkage. As described above, in the prior art, there is a problem in that only slight misalignment in attaching a sheet coil causes a large angular error. Also, although the angular error can be decreased if the precision of attaching a sheet coil and of incorporation thereof is improved, the cost is increased instead, wherein an original effect of becoming less expensive may be lost. It is therefore an object of the invention to provide an inexpensive resolver using a sheet coil, having only a small angular error, which can be downsized without resulting in a lowering of the detection voltage and can limit the variation in amplitude of flux linkage even if misalignment occurs when attaching a sheet coil.
The present invention is a means to solve the above-described problems and shortcomings, and a resolver using a sheet coil according to a first embodiment of the present invention is disclosed below.
That is, a resolver according to the present invention is provided with a disk-shaped rotor and two disk-shaped stators between which the rotor is placed with air gaps in the axial direction thereof, wherein the above-described rotor is such that a rotor side sheet coil is attached to both sides of a disk-shaped soft magnetic material on which are formed a secondary side pattern of a rotary transformer and a resolver excitation phase pattern, and a stator side sheet coil having a rotary transformer primary side pattern formed on a disk-shaped soft magnetic material is attached to one of the stators opposed to the above-described rotary transformer secondary pattern, and a stator side sheet coil having a resolver detection phase pattern formed on a disk-shaped soft magnetic material is attached to the other of the above-described stators opposed to the above-described resolver excitation phase pattern.
Also, the above-described rotor side sheet coil according to the present invention is formed of a single sheet composed of a disk having the above-described resolver excitation phase pattern formed, a disk having the above-described rotary transformer secondary side pattern formed, and a linear portion having a cross-over line that connects the above-described resolver excitation phase pattern and the above-described rotary transformer secondary side pattern to each other.
In addition, the above-described stator side sheet coil is formed of a single sheet composed of a disk having the above-described resolver detection phase pattern formed, a disk having the above-described rotary transformer primary side pattern formed, and a linear portion that links the corresponding two disks with each other.
Further, the above-described rotary transformer secondary side pattern formed on both sides of the disk according to the invention is a pattern eddying from outside to inside, and both the patterns are connected to each other in series, and the above-described resolver excitation phase pattern that is formed at both sides of the disk is a pattern eddying by 2N times in the circumferential direction where N is a natural number, and the center of the eddy on the surface side is disposed at the same position of the eddy on the rear side in the circumferential direction, and 4N eddies are connected to each other in series, wherein the axial multiple angle is NX.
Also, the above-described rotary transformer primary side pattern is formed on both sides of the disk, and both patterns eddying from outside to inside are connected to each other in series, and the above-described resolver detection phase pattern is formed on both sides of the disk, and one side of which is a xe2x80x9cxcex1xe2x80x9d phase and the other of which is a xe2x80x9cxcex2xe2x80x9d phase, wherein 2N patterns eddying in the circumferential direction are disposed, and the center positions of the eddies of the xe2x80x9cxcex1xe2x80x9d phase and xe2x80x9cxcex2xe2x80x9d phase slip by 90/Nxc2x0 from each other in the circumferential direction. Also, 2N eddies are connected to each other in series, wherein the axial angle becomes NX.
Therefore, in the present invention, because the area of the rotary transformer can be increased further than that of the prior art rotary transformers even if the outer diameter thereof is reduced, the detection voltage is lowered beyond that in the prior art. Also, because the patterns of the rotary transformer are not on the same level as that of the resolver patterns, no flux produced by the rotary transformer links with the detection phase patterns of the resolver, whereby a problem of the residual voltage can be solved, and it is possible to provide a resolver using a sheet coil, the angular error of which is further suppressed to be small. In addition, power consumption can be remarkably decreased, whereby it is very advantageous in an operation backed up by a battery in case of an electric failure.
Next, a resolver using a sheet coil according to a second preferred embodiment of the invention is disclosed below.
That is, in the present invention, one of either the outer diameter of the above-described rotary transformer secondary side pattern and that of the above-described rotary transformer primary side pattern is made larger than the other thereof.
Also, in the present invention, the radius r2 of the extremely outer conductor of the above-described rotary transformer secondary side pattern and radius r1 of the extremely outer conductor of the above-described rotary transformer primary side pattern is established so as 0 less than r2xe2x88x92r1xe2x89xa64xc3x97xcex2 or 0 less than r1xe2x88x92r2xe2x89xa64xc3x97xcex1 wherein the pattern pitch of the rotary transformer secondary side pattern is xcex2 and the pattern pitch of the rotary transformer primary side pattern is xcex1.
Next, a resolver using a sheet coil according to a third preferred embodiment of the present invention is disclosed below.
That is, in the present invention, the outer diameter of the above-described resolver excitation phase pattern is made larger than the outer diameter of the resolver detection phase pattern while the inner diameter of the resolver excitation phase pattern is made smaller than the inner diameter of the resolver detection phase pattern, or the outer diameter of the above-described detection phase pattern is made larger than the outer diameter of the above-described excitation phase pattern while the inner diameter of the detection phase pattern is made smaller than the inner diameter of the excitation phase pattern.
Also, in the present invention, where the pattern pitch of the resolver excitation phase pattern is xcexxcex8, and the pattern pitch of the resolver detection phase pattern is xcexxcex1, the radius rxcex80 of the extremely outer conductor of the resolver excitation phase pattern and the radius rxcex10 of the extremely outer conductor of the rotary transformer primary side pattern, or the radius rxcex81 of the extremely inner conductor of the resolver excitation phase pattern and the radius rxcex1i of the extremely inner conductor of the rotary transformer primary side pattern are established so as to become 0 less than rxcex1oxe2x88x92rxcex8oxe2x89xa64xc3x97xcexxcex1 and 0 less than rxcex8ixe2x88x92rxcex1ixe2x89xa64xc3x97xcexxcex1 or 0 less than rxcex8oxe2x88x92rxcex1oxe2x89xa64xc3x97xcexxcex8 and 0 less than rxcex1ixe2x88x92rxcex8ixe2x89xa64 xc3x97xcexxcex8.
Therefore, with the present invention, it is possible to limit the variation in amplitude of flux linkage even if misalignment occurs when attaching sheet coils, wherein the angular error can be minimized. In addition, because there is no need to remarkably increase the assembling accuracy, it is possible to provide an inexpensive resolver.